Exploring the Unknown UniverseDaniel Whiteson, UC Irvine

MotivationThe Standard Model

Can this be right?

Outline

I. MotivationII. StrategyIII. Results

Searching for new physicsModel

Search strategySpec

ific

Gen

eral

Our goals:- Maximize possibility for discovery- Learn something no matter what we see

Traditional approach

Bet on a specific full theoryOptimize analysis to squeeze out maximal sensitivity to new physics.

param 1

para

m 2 (param 3-N fixed at arbitrary choices)

Model

Search strategySpec

ific

Gen

eral

Model independent search

Discard the modelcompare data to standard model

Model

Search strategySpec

ific

Gen

eral

“Never listen to theorists. Just go look for it”

--Aaron Pierce, Theorist

Compromise

Admit the need for a modelNew signal requires a coherent physical explanation,

even trivial or effective

Generalize your modelFocus on the general experimental sensitivityConstruct simple models that describe classes of new physics

ExamplesSimple SM extensions: fourth generation, Z’, resonances (X->tt) etc

Model

Search strategySpec

ific

Gen

eral

Effective LagrangianA natural, compact language for communication between theory and experiment.

Experimental data

Full Theory

Full Theory

Full Theory

Full Theory

Full Theory

Full Theory

Limits or measurements

on effective Lagrangian parameters

A Theorist’s dream?Unfolded cross-sectionsDeconvolution to remove detector effects

Publish measured differential cross-sections

Theorists don’t need to know/have detector description

This is hard!

Outline

I. MotivationII. StrategyIII. Results a. Heavy resonances (Z’) b. Heavy quarks (b’, t’) c. Simplified SUSY

CDF

Dataset

High mass resonances

Z’ to di-muons

UCI UndergradEddie Quinlan

High mass dimuon res.

]2 [GeV/c!!M200 400 600 800 1000 1200

Even

ts

-210

-110

1

10

210

310

410

510

Data

*!Z/

tt

WW

Fakes

Cosmics

-1CDF Run II Preliminary 4.6 fb

]2 [GeV/cµµM200 400 600 800 1000 1200

(Obs’

d -

Exp’d

)/

Exp’d

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

-1CDF Run II Preliminary 4.6 fb

PRL 2011, to appear

Z’ to muons

PRL 2011, to appear

Z’ to muons

PRL 2011, to appear

Z’ to muons

]2

Z’ mass [GeV/c

200 300 400 500 600 700 800 900 1000 1100

) [p

b]

!!

!(Z

’) *

BR

(Z’

"

-310

-210

95% CL limit

IZ’

secZ’

NZ’

#Z’

$Z’

%Z’

SMZ’

-1CDF Run II Preliminary 4.6 fb

PRL 2011, to appear

ATLAS Z’ Penn +other groups

Limits Penn +other groups

Limits Penn +other groups

Outline

I. MotivationII. StrategyIII. Results a. Heavy resonances (Z’) b. Heavy quarks (b’, t’) c. Simplified SUSY

4th generationPDG says it’s

ruled out to 6σ....

4th generation

[GeV]d4-mu4m

-150 -100 -50 0 50 100 150

[G

eV

]4!

-ml4

m

-150

-100

-50

0

50

100

150 ) [%

]2"

#P

rob(

-110

1

10

projects.hepforge.org/opucem/

PDG says it’s ruled out to 6σ....

..that’s true if the masses are degenerate

t’Selection1 lepton

pt>20 GeV4 jets pt>20 GeV

Missing transverse energy >20 GeV

Sample4.6/fb

28

UC Davis

t’

Limitmt’ > 335 GeV

29

UC Davis

b’Selection2 like-signed leptons

pt>20 GeVat least one isolated

2 jets pt>20 GeV >=1 btagsMissing transverse energy >20 GeV

Sample2.7/fb

UCI UndergradMatt Hickman

PRL 104 091801 (2010)

b’Final selection2 like-signed leptons 2 jets >=1 btags

Missing transverse energy

PRL 104 091801 (2010)

mb’ > 338 GeV

b’ decaysIf b’ -> Wt

same-sign lepton selection: ~2%consider single-lepton mode

32

UCI undergradReza AmirArjomand

Signal (madgraph)

33

Number of jets0 2 4 6 8 10

Fra

ctio

n o

f E

ven

ts

0

0.05

0.1

0.15

0.2

0.25=300

b’m

=350b’

m

=400b’

m

CDF Run II Preliminary

[GeV]TH

0 200 400 600 800 1000

Fra

ctio

n o

f E

ven

ts

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

CDF Run II Preliminary

Eight hard partons, ~6 jets

Signal (madgraph)

34

Number of jets0 2 4 6 8 10

Fra

ctio

n o

f E

ven

ts

0

0.05

0.1

0.15

0.2

0.25=300

b’m

=350b’

m

=400b’

m

CDF Run II Preliminary

[GeV]TH

0 200 400 600 800 1000

Fra

ctio

n o

f E

ven

ts

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

0.18

CDF Run II PreliminaryHTScalar sum of transverse energy in the event

Includes jets, lepton and missing transverse energy

Captures soft recoil and unclustered jets

top quark pair backgroundtt + 0,1,2,3p p = udscbMadgraph+PythiaMLM matching

35

TJet-H

0 1000 2000 3000

Ev

ents

-210

-110

1

10

210Backgrounds

=350b’

b’, m

CDF Run II Preliminary

Analysis techniqueEventsheavy and jetty

Analysis variable

normalized to 5/fb36

5j6j 7j+

Data, >=1 b-tag

37

5j6j

7j+

The numbers

38

The limits

39

Direct searches

mb’ > 372 GeV mt’ > 335 GeV

replace

Direct searches

mb’ > 372 GeVIf BR(b’ →Wt)=100%

mt’ > 335 GeVIf BR(t’ →Wq)=100%

b’ l+j

b’ and t’

If mt’ > mb’

u c t t’d s b b’

PRL 2010, PRD 2011

UCI undergradMatt Kelly

UCI postdocChristian Flacco

b’ and t’

PRL 2010, PRD 2011

b’ and t’CDF limits

u c t t’d s b b’

PRL 2010, PRD 2011

b’ and t’

No direct limits!PRL 2010, PRD 2011

t’ and b’

mt’ = mb’ + 100 mt’ = mb’ + 50PRL 2010, PRD 2011

Limits

V44

V34

290300

PRL 2010, PRD 2011

heavy quarks

mQ’ > 290 GeV

If the lifetime is short enough so the decay is in the central detector:

PRL 2010, PRD 2011

ATLAS t’Selection2 OS leptons

pt>20 GeV2 jets pt>20 GeV

Missing transverse energy >20 GeV

Sample35/pb

UCI grad studentMichael Werth

topology

tb

Wt

b

W

Boosted tops

topology

tb

Wt

b

W

t’b

W

t’b

W

Boosted Ws!

Lepton-neutrino anglesHeavy t’ SM top

WMore W pT means smaller opening angle

Mass reconstructionAssume lepton and neutrino are ~collinear

Data

No sign of heavy quarks...

Limit

Limitmt’ > 275 GeV

Limit

Limitmt’ > 275 GeV

First LHC t’ li

mits

First t’ d

ilepton search

Dark MatterNeed long lived dark matter X

Dark Matter

Dark Matter XSM ParticlesSM Charges Dark Charge

Need long lived dark matter XGive it some dark charge that is conserved(eg R-parity for susy LSP)

Dark Matter

Dark Matter XSM ParticlesSM Charges Dark Charge

Need long lived dark matter XGive it some dark charge that is conserved(eg R-parity for susy LSP)

X can’t be light (~< 10 GeV) and carry SM charges to be consistent with relic density.

Dark Matter

Dark Matter XSM Particles

Connector Y

SM Charges

SM Charges

Dark Charge

Dark Charge

Need long lived dark matter X

Produce Y, decay as Y -> f X

Dark Matter+4th genUCI grad studentKanishka Rao

Look for ttbar + invisible XT’ -> t+Xstop -> t + LSP

Transverse mass

Limits

Outline

I. MotivationII. StrategyIII. Results a. Heavy resonances (Z’) b. Heavy quarks (b’, t’) c. Simplified SUSY

SUSY

GoalSet limits on SUSY-like processes in as general a fashion as possible

ApproachUse effective lagrangian, explicitly set particle masses (EW scale):

simple to handle, easy to interpret

Set limits as functions of these masses, not parameters of specific models: can be easily translated into arbitrary models

How?How many particles & parameters needed?Want leptons needs Ws and Zs, so chargino/neutralinos and sleptons

Want strong production so squarks and gluinos

R-Parity conserving need LSP

Large sections of this space are 3 or 4-dimensional

SUSY simplified UCI postdocNing Zhou

SS SUSY simplified UCI postdocNing Zhou

CDFStill producing world-class physics

ATLASWorking well, much more to come